Haig Sutherland was the first person to be cast. Elizabeth Banks was the second. Gregg Henry was the last actor to be seen for the part (out of more than one hundred actors from Los Angeles and Vancouver) and nailed his audition. Nathan Fillion was the last actor to be cast, about a week before shooting began. Shooting lasted forty-seven days.
Dangled above the street at the beginning of the film, and on stage later at the Deer Cheer celebration, you can see a "Henenlotter's Saddle Lodge presents Deer Cheer" sign, a reference to cult horror Writer and Director Frank Henenlotter, famed Creator of Basket Case (1982) and Brain Damage (1988).
The trivia items below may give away important plot points.
The post-credits coda shows a cat getting possessed by the last surviving creature. In an early draft, this was meant to happen to Bill (Nathan Fillion), after the Grant-creature is destroyed. Starla (Elizabeth Banks) sees the resulting wound later, prompting her to shoot Bill to death.
Jenna Fischer disclosed on a television talk show that she got the role of Shelby as a "birthday present" from her spouse, James Gunn, after another actress dropped out of the movie. Being a big fan of zombie films, she always wanted to play a zombie. Upon hearing the news, she screamed with joy.